Urological complications of colorectal cancer during surgery of the large bowel are relatively frequent. Fortunately these complications are as a rule transient and recede either spontaneously or after a suitably selected therapeutic procedure. Permanent complications account in our group comprising 311 patients only for a fraction of a per cent. The problem of carcinoma of the colon and rectum and treatment, along with possible complications, is becoming increasingly important in particular in conjunction with an objectively assessed shift of the prevalence of the disease to younger age groups. The group of patients treated in the authors' department on account of colorectal carcinoma during the last five years was evaluated in detail and thus it was possible to detect why different complications developed. This evaluation of all recorded cases was made from the diagnostic aspect as well as with regard to therapeutic possibilities, taking into account the technique of surgical approaches.